Hydraulic transmission



Nov. 1, 1938.

R. DINZL HYDRAULIC "IRANSMIS SION 3 Sheets-Sheet 1 Original Filed June12, 193') INVENTOR= NOV. 1, 1938. h I R w z 1 2,134,707

HYDRAULIC TRANSMiSS ION Original Filed June 12, 1950 s Sheets-$heet 2 l1 i i n v q i 1 I I -qr nu #a z 1 v 1 i I' NvENToR.

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NOV. 1, 1' R. DINZL a .HYDRAUIJIC TRANSMISSION ori inal Fileduune lz,1930 s Sheets-Sheet 3 INVENTO'R cHARn W. 19122122,,

Patented Nov. ,1, 1938 e PATENT orFicE- nrnnauuc TRANSMISSION Richard W.Dinzl, Nan-berth, Pan, assignor, by

mesne assignments, to Baldwin-Southwark Corporatlon, a corporation ofDelaware Application June 12, 1930, Serial No. 460,626 Renewed June 26,1935 a 13 Claims. (o1. 60-52) My invention relates generally tohydraulic transmissions, particularly materials testing apparatus, and.it is one object of my invention to provide an improved combination foreffecting a substantially constant rate of strain in'a speci-J men.Different materials have their own stressstraincharacteristics, andthese characteristics may be influenced by varying the rate at which aspecimen is strained during atest. As a result, different tests of thesame material may indicate different characteristics depending upon thespeed with which the operator loads the specimen, thus causing confusionand possible misunderstanding as to the true characteristics of thematerial. To maintain a substantially con-' stant rate of strain whenusing a hydraulic testing machine, it is necessary not only to vary thehydraulic pressure of the load producing mechanism but also to vary thequantity of iluid supplied thereto.

It is a further object of my invention to accomplish a uniform rate ofspecimen strain with a combination of elements that is relatively sim-:ple and economical in construction and operation and that is positiveand dependable over a wide load range and under wide variations in thedeformation of the specimen.

;In the specific aspect of the'invention I accompli sh the foregoingobjects by'providing in combination a materials testing machine having ahydraulically actuated'load producing cylinder and ram supplied withfluid from a continuously operable variable displacement pump,preferably of the Hele-Shaw type, together with a spring loadeddiaphragm for controlling the rate of dischargefrom the pumpautomatically in accordance with a predetermined pressure differentialon opposite sides of an 'adiustable orifice,

the lower pressure being that in the load produc- 1 ing cylinder and thehigher pressure'that of the pump, whereby any momentary variation in thepressure differential will immediately eifect adjustment of the springloaded diaphragm thereby to adjust the pump discharge and accordinglyalso adjust the pump pressure so as to reestablish the, desired pressuredifferential. There is thus eflectedga substantiallyconstant rate of rammovement and accordingly specimenstrain Iii of Fig. l.

but for purposes of the present invention these factors need not beconsidered.

A further object of my invention is to provide improved means forcontrolling the press speed without regard to -the resistance of thespecimen 5 undergoing test, that is to'say, to maintain the same speedof a driven element at low or high readings of the pressure gauges. v

These and other features of my invention are more fully describedhereinafter: reference being had to the accompanying drawings, in which:

Figure 1 is a fromelevational view of one form of testing apparatus withwhich the improved controlling means forming the subject of my inventionmay be employed, certain portions being broken away to show thearrangement of parts and details of. construction, such as the controlvalve E and its hand wheel which are turned sidewise to show clearly anddiagrammatically their relation to the other elements.

, Fig. 2 is a plan view of the same, partly broken view of the variablepressure diagrammatically showing thedifferential pressure pipes El andII in dottedlines, and

Fig. 5 is an elevational view of a regulating or controlling valve ofthe needle type partly broken away to show details of construction.

In the .drawings, A represents the frame of a materials testing machinehaving an overhanging head portion A. The machine is of the wellknownEmery type such as disclosediin Emery Patent No. 1,846,468, although theinvention is of course applicable to other types of hydraulic materialstesting machines having in general a hydraulic load producing ram D andcylinder D for actuating the load producingframeA. Below suchoverhanging head portion and in alignment there 1 below the latter is atable 0 which is connected to and is movable with the overhanging headportion A. The overhanging'head portion and the cross-head are recessedfor the reception of the usual wedging grips between which test piecesundergoing tensile strains may be held. Test pieces undergoingcompression strains are mounted between the table C and theadjustable-crosshead B. A cross-head B in either tension or compressiontests transmits the specimen load to a cylinder D containing a movableram D to which such frame portion is connected; delivery of such fluidpressure being under the control of a by-pass valve E which may beoperated by a hand wheel E. The delivery of such fluid pressure iseffected by the operation of a continuously acting pump of the variabledischarge rotary piston type, of which the Hele-Shaw pump is awell-known example and for present purposes may be considered as thetype of pump employed. This pump, indicated at I, may be driven by anelectric motor 2 whose operation may be controlled by the switch buttons(1 and b.

The base of the testing apparatus includes a tank or reservoir F forfluid, usually oil. The pump is provided with a suction pipe F andleading from the pump is a pipe G which communicates with a pipe H inwhich the by-pass valve E is located; the pipe H leading to thereservoir F. A regulating valve J, which may be of the needle type andof which an example is indicated in Fig: 5, is mounted in the line Gjust above the pump casing, and at a convenient point, which may be justabove this valve, a pipe K is connected through which the fluid pressuremay be directed to the cylinder D. In addition a pipe L, connected tothe line G, is provided with a relief valve L through which excesspressure may bleed to the reservoir F via pipe L In the operation ofpumps of this type, the

relative position of the pistons or plungers is controlled by a floatingelement, usually a ring, movably mounted with respect to the cylinder ofthe. pump casing; such ring being indicated at 3, Fig. 4. This floatingring is supported. within the body or casing 4 of the pump in suchmanner, as indicated in Fig. 4, that motion may be imparted to it todetermine the desired eccentricity with respect to the rotating memberhaving the recesses in which the pistons or plungers of the pump workand therefore theamount of fluid passed to the cylinder D containing theram D' which in turn efi'ects movement of the member or members servingto stretch or compress'the test pieces. Whenthe floating ring whichcontrols the position of the pistons is centrally posed with respect tothe cylinder of the pump casing, the relative position of the pistonsremains unchanged during revolution of the member carrying the same andalthough the pump is running the plungers or pistons have no stroke andit is doing no effective work. 'When, however, the floating ring ismoved with respect to the cylinder of the pump; the member carrying thepistons or plungers being rotated by a prime mover such as the motor 2,the relation of the pistons or plungers" with respect to the cylinder tothe left effects changes in the stroke of the plungers or pistons, oneof which is indicated at I. In the operation of the testing machineaccording to my present invention, I desire to control the press speedwithout regard to the resistance of the specimen; that is to say, tomaintain the same speed at low or high readings of the press gauge (orgauges).

' The pump I may be driven by the direct connected motor 2 and in thepresent instance actuating mechanism for the floating ring 3 is disposedat each end of the pump casing. In the usual operation of pumps of thistype there will be no pumping action until motion has been imparted tothe floating ring. In the present instance the floating ring has beendisplaced toward theleft, as indicated in Fig. 4. The floating ringcarries relatively disposed members 5 and 6 which project throughopposite walls of the pump casing; the member 5 being provided with athrust pin 1 to which motion is imparted for the purpose of shifting thefloating ring in a manner hereinafter described, while at the oppositeside of the pump casing an elastic member, which may be a spring 8, ismounted, preferably in the shell 8 which spring serves to keep thethrust pin 1 of the floating ring actuating mech-' anism in contact withits controlling member so as to be immediately responsive to any movement of the same.

The speed at which the press is operated may be regulated by operationof the valve J set in the line G through which fluid is delivered by thepump and this valve controls the volume of fluid delivered. This valveis set before a testing operation begins, in order that the volume ofdelivery and the speed of the ram may 'be constant. The line G throughwhich fluid is delivered by the pump is connected via pipe 9 with oneside of a spring loaded diaphragm l0, while the discharge of the pump isconnected via pipe II with the opposite side of this diaphragm, and aconstant differential, which may approximate one hundred (100) pounds ismaintained on opposite sides of said diaphragm; the greater pressurebeing delivered via thepipe II. The diaphragm I0 is mounted at one endof a chamber formed in a suitable casing l2 and is operatively'connected to a rod l3 lying in engagement with the thrust pin 1connected to the floating ring 3. This diaphragm is under the influenceof an actuating spring l4 mounted on that side of the diaphragmreceiving pressure via the pipe 9, and the pressure exerted by'thisspring may be reg ulatedto some extent by a set screw l5.

The function of the spring I4 is to supplement the force of the lowpressure fluid so as to balance the force of the high pressure fluidwhereby in the event that resistance of the specimen should increase sothat there is an increase of pressure on the low pressure side, thenthis increased low pressure together with the force of the spring willcause adjustment of the pump to increase the discharge thereof andaccordingly increase the pressure on .the high pressure side, thusreestablishing a new balance between the forces acting on opposite sidesof the diaphragm. Conversely when the strain of the specimen becomes sogreat as to cause a reduced load, such as passing through the yieldpoint, then the pressure in the load producing cylinderXwill dropresulting in a reduced pressure force on the spring side 'of thediaphragm and thereby permitting the fluid from the high pressure sideto'move the diaphragm toward the right and accordingly reduce thedischarge from the pump until the predetermined pressure diflerential isestablished. It will be understood that the diaphragm ill in moving ,therod l3 causes the latter to react 'upon the thrust pin 1 oi'the floatingring and impart iull movement to the same within the cylinder of thepump casing (such movement being to the left in the present instance) sothat when the pump starts to operate it is at full stroke. In theinitial position and before the motor is started,

the floating ring has been moved by the'springthe spring 8 to return thefloating ring to position for the deliveryof the desired volume of fluidwhich may be directed to the cylinder Dto eflect the testing operation.When the bypass valve E is open and the pump is runningthe fluid issimply circulated by the pump into and out of the tank via the pipes (3iand H, and-the by-pass valve E. Leading from the pipe Gds the line Ksaid cylinder.

connected to the cylinder D and the line L normally closed by thespring-loaded relief valve L. The needle valve J, controlling the volumeof flow-delivered by the pump, isset before atesting, operation begins.When the by-pass valve E is closed the, fluid pressure delivered by thepumppasses to the cylinder D, past the needle regulating valve J, vialine K, and builds up in At the same time pressure passes via pipe 9 tothe diaphragm l0 and with the spring i4 effects movement of the floatingring of the pump; to the left as viewed in Fig. 4. When the pressurereaches the point at, which the relief valve is setywhich may be justshort of the total movement of the rain in the cylinder opens andpressure may'bieed back to the tank and at the same time the pressure onopposite sides of the diaphragm changesyincreasing on one side bypressure delivered via pipe H and overcomming the pressure delivered viapipe 9 and that exerted by the spring I4 and the pump slacke'ns. 1

It will be understood of course that fluid fills the several lines whilethe circulating period conwith the overhanginghead A.

tinues', during which time the test specimen may be set in place either'betweenthe overhanging head A and thefladjustable cross-head B, orbetween the latter and the 'table C which moves After the test specimenhas been set in place, the by-pass valve E is closed and the pressurethen delivered by ready to open the by-pass valve should the gauge (orgauges) indicate the maximum pressure for which-the machine has beendesigned, in case the specimens do not. fall before such maximum isreached. During the operation of the pump, the constant diflerential ismaintained between the opposite sides of the diaphragm, and the floatingring'of the pump is held in position to insure delivery of such pressureat a constant rate. Should overloading occur, the relief valve L willopen and permit the pressure to bleed into the reservoir F in case theoperator does not open the by-pass valve promptly. As soon as theby-pass valve is opened, the ram carrying the head and table is free tomove inthe cylinder; the continued operation of the pump displacing thefluid in the cylinder by which such ram has been moved; the overhanginghead and table of the testing apparatus return to the non-operativeposition, and the spring-loaded diaphragm moves the floating ring to thefull stroke position in the pump casing.

I While the fluid pressure is being delivered to the cylinder D duringthe application of the straining or compressing force applied to thespecimen undergoing test, the floating ring will be held in suchposition that the pump will deliver a constant volume of fluid to insurea constant speed of the ram independent of the resistance of thespecimen under test by reason of that fact that the higher pressureapplied to one side of the diaphragm properly balances the loadingspring II on the opposite side or. the diain effecting a testingoperation, such relief valve i invention as set forth in the appendedclaims.

phragm in connection with the lower pressure delivered thereto. Whileboth sides of media-- phragm are exposed to pressure it is under a con-'stant differential and any resistance developed by reason of thepressure oi the specimen reacts through pipe 9 and the pump pressureimmediateiy builds up to resist It will of course be understood thatvarious changes in' details of construction and arrangement of parts maybe made by those skilled in the art without departing irom the spirit ofthe I claim: 1.. The combination with the cylinder of hydraulicapparatus, a ram movable therein, a variable discharge rotary pistonpump of the Hele- Shawtype having stroke adjusting means in-, cluding afloating element controlling the relative position of the pistons offsaid pump,'and 'a line providing fluid communication between said pumpand cylinder through which pressure may be delivered to effectmovementoi the ram, of a the pump passes the valve J via line G andpipe, K to the cylinder containing the ram, to which the movable headand table are connected, and

the ram is moved at a constant speed determined by the extent of openingor the regulating valve J. When the test is completed, the by-pass valvemay be -flrst opened and then the. motoris stopped. While both sides ofthe diaphragm are exposed to pressure, one side communicating with thepump and the other with the line of fluid delivered by the pump, thereexists a'constant differential across the opening provided by the casingoperatively connected to the pump mechanism, a spring-loaded diaphragm.disposed in said casing and having its opposite sides in communicationwith pressure delivered by said pump, means operatively disposed betweensaid diaphragm and the floating element for moving the latter in onedirection by the actiorrof said diaphragm, means tending to move thefloating element against the action of said diaphragm, and a valve inthe delivery line of the. pump for controlling the pressure delivered toone side of said diaphragm.

2. Thecombination with the cylinder of hydraulic apparatus and a rammovable therein,

latter being in fluid communication with said cylinder and deliveringpressure thereto to eflect movement ofsaid ram, 9. spring-loaded.diaphragm, means operatively disposed between said diaphragm and saidfloating element for actuating the latter in one direction, means for:delivering pressure to opposite sides of said diaphragm to maintain aconstant difierential, a valve for controlling the pressure delivered toone side of said diaphragm, and means tending to hold said floatingelement in neutral position.

3. The combination with the cylinder 01 bydraulic apparatus, a rammovable therein, a variable. discharge rotary piston pump of the Hele-Shaw type having strokes-adjusting means including a floating elementcontrolling the relative position of the pistons of said pump; a'lineproviding fluid communication between said pump.

and cylinder through which pressure may be delivered to effect movementof the ram, of a cas- V ing operatively connected to the pumpingmechanism, a spring-loaded diaphragm mounted in said casing, a linedelivering pressure directly from the pump to a chamber at one side ofsaid diaphragm, a connection from the pump line de-' livering pressureto a chamber at the other side of said diaphragm, means operativelydisposed between said diaphragm and the floating element for moving thelatter in one direction by the action of said diaphragm, a springtending to move the floating element in the opposite direction againstthe action of said diaphragm, and a valve in the delivery line of thepump for controlling the pressure delivered to one side of saiddiaphragm.

4. In pumping mechanism for hydraulic appa-r ratus, the combination ofcontinuously operating variable volume pumping mechanism of the Hele-Shaw type having stroke-adjusting means, and means for controlling saidvariable volume pump- ,ing mechanism comprising a pressure-operateddiaphragm operatively connected to the strokeadjusting means of the saidpumping mechanism, a casing enclosing said diaphragm, a springinterposed between a wall of said casing and one side of said diaphragmfor loading the same, means providing for fluid communication betweenopposite sides of said.diaphragm and the delivery side of said variablevolume pumping mechanism whereby fluid under difiering pressure may bedirected 'to opposite sides oi said stroke of said ram, mechanism foradjusting the stroke of the pump pistons, a passage providing fluidcommunication between said pump and cylinder for effecting movement ofthe ram, and fluid pressure means for automatically controlling saidstroke adjusting mechanism to effect a substantially predetermined rateof ram movement during variations in the fluid pressure force requiredto effect said ram movement.

6. The combination with a cylinder for hydrl aulic i apparat s-gm ram""movable therein "at a i r elativelyfslow rate whilesubjected' to'a'v'arying e's'i'stan'ce against inovemnw" a continuouslyoperating-variable discharge rotary piston pump in' which the pistonstroke may be {varied during :saidw continuousiaoperation I and during a{single stroke of said ram, mechanism for adjusting the stroke of thepump pistons, a passage providing fluid communication between said pumpand cylinder for effecting movement of the ram, a throttling orifice insaid passage for efiecting diflerential pressures in said passagewhereby the higher one of said difierential pressures is that of thepump and the lower pressure is that of the ram cylinder, and fluidpressure means responsive to said difierential pressures for directlycontrolling and operating said stroke adjusting mechanism to effect asubstantially constant rate of movement of said ram.

7. The combination set forth in claim 6 further characterized in thatsaid means for controlling the stroke adjusting mechanism includes amovable element whose opposite sides are subjected respectively to thedifferential pressures.

8. The combination set forth in claim 6 further characterized in thatsaid orifice is adjustable, whereby said controlling means automaticallyeifects adjustment of the piston stroke so as to increase the pumpdisplacement for larger openings of the orifice and to decrease the pumpstroke for smaller openings of'the orifice thereby to vary the rate ofram movement.

9. The combination set forth in claim 6 further characterized in thatsaid means for controlling the stroke adjusting mechanism includes adiaphragm whose opposite sides are subjected to said differentialpressures, and means for producing a force constantly acting on one sideof said diaphragm to supplement the pressure force on that side wherebya substantially constant pressure differential is maintained on oppositesides of said orifice.

10. A hydraulic transmission, comprising a hydraulic motor, a pumpconnected to said motor,

for delivering liquid thereto to drive the same, a choke connected inseries with said motor, and means responsive to the drop in pressureacross said choke for varying the relative displacements of said pumpandsaid motor to thereby maintain the speed of said motor substantiallyconstant.

11. A hydraulic transmission, comprising a hydraulic motor, a variabledisplacement pump connected to said motor for delivering liquid theretoto drive the same, a choke connected in series with said motor, andmeans responsive to the drop in pressure across said choke for varyingthe displacement of said pump to thereby maintain the speed of saidmotor substantially constant.

12. -A hydraulic transmission, comprising a hydraulic motor, anadjustable variable delivery pump connected to said motor for deliveringliquid thereto to drive the same, a choke of normally fixed flow areacommunicating on one side with said motor and on the other side withsaid pump, and. means responsive to variations in pressure across saidchoke for adjusting the operation of said pump to vary the delivery offluid therefrom to said motor so as to maintain the speed of said motorsubstantially constant during variations in the pressure across saidchoke. I

13. The combination with a cylinder for hy- Vdraulicapparatus, a rammovable the'reinat a relatively slow rateiwhile-subjected to a varyingresistance --against movement, a continuously aoperatingyariabledischarge rotarypiston pump in which the-piston stroke may be variedduring saidgcontinuous operation and during a single strokeof said ram,mechanism for adjusting the mayo? I stroke 01' the pump pistons, apassage providing fluid communication between said pump and cylinder foreffecting movement or the ram, fluid pressure means including athrottling orifice in' said passage for automatically controlling saidstroke adjusting mechanism to effect a substantialiy predetermined rateof ram movement during variations in the fluid pressure force' required

